1. Field of the Invention
The present invention relates to a taking lens for television photography.
2. Related Background Art
In a conventional broadcast television camera system, a communication is perfomed by using analog signals for the interface between a camera and a lens. For example, a lens unit is controlled by supplying a television taking lens with voltages which determines the positions of a focus lens and an iris and the speed of a zoom lens, and conversely, information of the lens unit is notified to the camera unit by transmitting voltages which indicates the positions of the focus lens, zoom lens, and iris.
Analog servo control of the taking lens is performed by using a feedback system having a potentiometer as a position sensor.
There are limits in increasing the number of types of analog signals and in a precision of analog signals. From this reason, a current tendency is that a serial interface is used for providing a communication function between a camera and a lens.
As the communication function is realized by the serial interface, a case of using CPU is uncreasing and the digital servo used with CPU is prevailing.
If the position of a lens is detected through constituted digital servo, an output of a potentiometer is required to be A/D converted. If a high resolution is necessary, an expensive A/D converter having a high resolution function is used.
Since the size of an encoder of an absolute value output type is large, an encoder of a relative value output type is used. However, since the absolute position of a lens cannot be known from the relative value output, it is necessary to perform an initializing operation of moving a lens to a reference position in order to detect the absolute position of the lens.
According to one aspect of the invention, an optical device is provided which has information means for generating or determining information on the basis of a necessary initializing operation and communication means for communicating with a camera mounted on the optical device, the optical device comprising: initializing means for executing the initializing operation; and communication inhibiting means for inhibiting the communication by the communication means until the initializing means completes the initializing operation. The optical device can prevent improper communication from being executed.
According to one aspect of the invention, an optical device is provided which has movable optical means, signal generating means for forming a signal change corresponding to a motion of the optical means, position information generating means for generating position information by forming a signal corresponding to the number of signal changes formed by the signal generating means, and communication means for communicating with a camera mounted on the optical device, the optical device comprising: initializing means for moving the optical means to a reference position so as to convert the position information generated by the position information generating means into absolute position information; and communication inhibiting means for inhibiting communication by the communication means until an initializing operation by the initializing means is completed. The optical device can prevent improper communication from being executed.
According to one aspect of the invention, a system is provided which has a photographing optical apparatus having information means for generating or determining information on the basis of a necessary initializing operation and a camera mounted on the photographing optical apparatus, the system comprising: communication means for performing communication between the photographing optical apparatus and the camera; initializing means for performing the initializing operation; and communication inhibiting means for inhibiting the communication by the communication means until the initializing means completes the initializing operation. The system can prevent improper communication from being executed.
The other objects of the invention will be become more apparent from the detailed description of embodiments when read in conjunction with the accompanying drawings.